code: def _on_new_preroll_streaming(self, appsink):
      # print('preroll')
      chunk = appsink.emit("pull-preroll")
      self._streaming_queue.put(chunk)
  
file_path: TimeSide/timeside/core/encoder.py
imports: from timeside.core import Processor, implements, interfacedoc, abstract
  from timeside.core.api import IEncoder
  from .tools.gstutils import numpy_array_to_gst_buffer, MainloopThread
  import gi
  from gi.repository import GLib, Gst
  import threading
label_desc: Use image node_id 7 for calling the GstEncoder obj's underlying member method code with example usage: obj._on_new_preroll_streaming(appsink) without return types